1. Field of the Invention
The present invention relates to a processor card. More specifically, the present invention discloses a processor card that can be hot swapped in and out of a PCI hot swap bus.
2. Description of the Prior Art
In many fields, such as in telecommunications and network servers, computing equipment downtime is simply unacceptable. Nevertheless, failures occur and to ensure that the downtime is kept to an absolute minimum, certain design techniques have been adopted. For example, motherboard design concepts have been abandoned for a passive backplane architecture. A passive backplane is simply a circuit board with an absolute minimum amount of circuitry, with slots into which other circuit boards are plugged. Since a passive backplane has, ideally, no circuitry on it, its mean time between failures (MTBF) is considerably longer than a motherboard. An appropriately designed processor card plugs into its processor slot on the backplane. Similarly, add-on cards plug into their add-on-card slots on the backplane. In this manner, via traces on the backplane, the processor and its associated bus circuitry are connected to the add-on cards.
When either an add-on card or a processor card fails, the card is simply unplugged from the passive backplane and a replacement is inserted. The entire process is relatively quick and easy, which would not be the case if a motherboard architecture had been adopted and it was the motherboard itself that had failed. The catastrophic equivalent of this using a passive backplane architecture is the backplane itself failing. This, however, is highly unlikely as the passive backplane has no active onboard circuitry.
Although the above swapping technique is quite quick, it used to be necessary that any card, processor or add-on, be cold swapped. That is, the computing equipment had to be powered down, and then the card could be removed and replaced. Unfortunately, powering down such equipment, and powering it back up, forced the entire device to go offline when, perhaps, only a relatively minor card needed to be replaced. Furthermore, powering up the computing equipment often entails a relatively lengthy booting procedure before the equipment comes back online. Consequently, hot swapping techniques were developed. Such techniques enable an add-on card to be swapped from the bus without powering down the computing device. The other elements, the processor card and properly functioning add-on cards, could continue to operate and thus continue to provide a service, albeit with a reduced functionality. With the defective card replaced and brought back online, full functionality would return to the computing device.
The current standard for hot swapping add-on cards from a PCI bus is defined by the so-called Compact PCI Hot Swap Specification. This standard was developed by a consortium, the PCI Industrial Computers Manufacturing Group (PICMG), and was made public in a release, PICMG 2.1 R1.0.
Please refer to FIG. 1. FIG. 1 is a function block diagram of a PCI hot swap bus 10, which is used as a server that controls a RAID hard disk array. The PCI hot swap bus 10 comprises a processor slot 11 into which is plugged a processor card 20, and a plurality of add-on-card slots 12 into which are plugged various add-on cards. Some of the add-on cards may be I/O cards 14 that establish communications with external devices, such as modems. Other add-on cards may be network cards 16 to establish communications across a network, or SCSI cards 18 to communicate with SCSI devices. Other types of cards may, of course, be plugged into the bus 10. Each card is connected to a corresponding slot via a connector 13. Excepting the processor card 20, every card on the PCI hot swap bus 10 comprises power switching circuitry 15, signal switching circuitry 17, and PCI circuitry 19 dedicated to fulfilling the specific functionality of the card. The power switching circuitry 15 is used to individually control power to each card. The power switching circuitry 15 may be manually controlled, or may be controlled by another device on the bus 10, such as the processor card 20. The signal switching circuitry 17 is used to electrically connect and disconnect the card from signal lines of the bus 10. The signal switching circuitry 17 is of critical importance when hot swapping a card, as it prevents transients from disrupting other cards on the bus 10, and performs appropriate hardware interfacing protocol functions when an add-on card is being inserted into, or pulled from, an add-on-card slot 12.
The processor card 20, however, is special in the prior art PCI hot swap bus 10. It has neither power switching circuitry nor signal switching circuitry. Instead, it has a processor 25 and PCI circuitry 27. The PCI circuitry 27 interfaces the processor 25 with the PCI hot swap bus 10, and also improves the fan-out capabilities of the processor card 20, allowing it to interface with more-add-on cards on the bus 10. In this example, the processor card 20 is used to control a RAID control circuit 40 for an array of hard disk drives 42. The RAID control circuit 40 controls the hard disk drives 42 to fetch and store information.
Finally, a power control circuit 30 supplies power to the PCI hot swap bus 10, and it is from this power control circuit 30 that each of the cards in their respective slots 11, 12 obtains electrical power.
Although all the add-on cards 14, 16 and 18 may be hot swapped from their add-on-card slots 12, the processor card 20 is, again, an exception. Because the processor card 20 lacks both the signal switching circuitry and the power switching circuitry of the other cards, it cannot be hot swapped from the processor slot 11. It lacks the necessary hardware to conform to the PCI hot swap specifications. Moreover, hot swapping a processor card 20 is generally considered impossible because the processor card 20 usually controls many of the signal lines 10 on the bus that the other cards require to function properly.
Nevertheless, being unable to hot swap the processor card 20 of the prior art is a severe drawback that leads to expensive downtimes in systems where any downtime at all is considered intolerable.
It is therefore a primary objective of this invention to provide a processor card that can be hot swapped from a PCI hot swap bus so as to prevent downtime in critical systems.
The present invention, briefly summarized, discloses a processor card that plugs into a processor slot on a PCI hot swap bus. The processor card has a connector for plugging into the processor slot, signal switching circuitry electrically connected to the connector, power switching circuitry for controlling power to the processor card and a processor electricallyxcx9cconnected to the signal switching circuitry. The power switching circuitry allows power to be selectively delivered to the processor card, and the signal switching circuitry enables the processor card to be hot swapped in and out of the PCI hot swap bus.
It is an advantage of the present invention that a malfunctioning processor card can be swapped out of the bus without needing to power down other components on the bus. Consequently, downtimes are reduced, and, with a preferred embodiment of the present invention, no downtime at all need be suffered.